II. Structures
There are two main structures that are important to libpng, png_struct and png_info. Both are internal structures that are no longer exposed in the libpng interface (as of libpng 1.5.0).

The png_info structure is designed to provide information about the PNG file. At one time, the fields of png_info were intended to be directly accessible to the user. However, this tended to cause problems with applications using dynamically loaded libraries, and
as a result a set of interface functions for png_info (the png_get_*() and png_set_*() functions) was developed, and direct access to the png_info fields was deprecated..

checking for pkg-config... /usr/bin/pkg-config
checking pkg-config is at least version 0.9.0... yes
checking for FONTCONFIG... yes
checking for FRIBIDI... yes
checking for SQLITE3... yes
checking for PNG... no
configure: error: Could not find a required library. Please see the README for your platform.

* QA Notice: The following files contain writable and executable sections
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* For more information, see http://hardened.gentoo.org/gnu-stack.xml
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* Note: Bugs should be filed for the respective maintainers
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* RWX --- --- usr/lib64/xbmc/xbmc.bin